1. Field of the Invention
The present invention relates to a high-frequency module including a plurality of filter elements.
2. Description of the Related Art
Mobile devices and the like having a wireless communication function include a filter circuit to transmit only high-frequency signals having a desired frequency and to attenuate high-frequency signals having frequencies other than the desired frequency.
For example, Japanese Unexamined Patent Application Publication No. 2012-109818 describes a filter circuit including a plurality of SAW filters. Specifically, the filter circuit in Japanese Unexamined Patent Application Publication No. 2012-109818 has an input terminal and an output terminal between which a plurality of SAW filters are connected in series with each other. Respective SAW filters are also connected between a connection line that connects the series connected SAW filters to each other and ground.
In the filter circuit described in Japanese Unexamined Patent Application Publication No. 2012-109818, an inductor or a series circuit including an inductor and a capacitor (referred to as a correction circuit) is connected in parallel to the series circuit of SAW filters in order to improve attenuation characteristics outside a pass band. In this case, the correction circuit is adjusted so that a high-frequency signal (a signal to be suppressed) outside the pass band which propagates through a circuit unit composed of SAW filters and a signal to be suppressed which propagates through the correction circuit have the same amplitude and opposite phases. Thus, the signals to be suppressed are canceled at a connection node between the circuit unit composed of SAW filters and the correction circuit, and are not output from the output terminal.
However, the configuration described above requires a correction circuit composed of an inductor or a series circuit including an inductor and a capacitor, separately from a main circuit unit composed of SAW filters having a filter function, only in order to improve attenuation characteristics.
Accordingly, the filter circuit has a large number of components, resulting in an increase in the size of the filter circuit, which is not suitable for current mobile terminals and the like where compactness is required.